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March 16, 2026Open Access

Semi-continuous cultivation of Nannochloropsis oceanica enables robust brewery wastewater treatment under variable wastewater composition and improves biomass lipid accumulation

Key Points

The aim is to assess the impact of brewery wastewater composition on the treatment performance of Nannochloropsis spp. using a semi-continuous feeding strategy.
Collected brewery wastewater at five time points throughout the annual production cycle.
Compared Nannochloropsis spp. growth in batch mode versus semi-continuous operation.
Measured nitrogen, phosphorus, and COD removal efficiencies along with biomass lipid content.
Achieved up to 100% nitrogen and 89% COD removal in semi-continuous operation.
Stabilized biomass production with lipid content increasing from 44.4% to 56.7% DW compared to batch cultivation.
Demonstrated effective growth even under variable COD conditions using a semi-continuous approach.

Abstract

This study investigates the effects of time-dependent changes in brewery wastewater (BWW) composition on the treatment performance of Nannochloropsis spp. and evaluates a semi-continuous “fill-and-draw” feeding strategy to mitigate fluctuations in wastewater composition. BWW was collected at five distinct time points in the brewery's annual production cycle (referred to as Collections 1–5, C1-C5) and evaluated for microalgal treatment under batch and semi-continuous operation. In batch mode, three species ( N. oceanica , N. gaditana , N. limnetica ) grew on moderate-COD BWW (C1-C4, 3.05–6.45 g L −1 COD), producing 0.66–1.21 g L −1 biomass and achieving high nitrogen (84–100%), phosphorus (68–97%), and COD removal (55–81%). Nannochloropsis spp. displayed mixotrophic pathways, utilising up to 0.98 g C-sugar g −1 C-biomass and capturing up to 0.96 g C-CO 2 g −1 C-biomass (or 1.30 g CO 2 L −1 wastewater). A high-COD BWW (C5, 16.67 g L −1 COD) inhibited growth in batch mode. However, semi-continuous operation ( N. oceanica ) transitioning from C1 to C5 facilitated physiological acclimatisation and mitigated high-COD growth inhibition, sustaining 0.92–1.28 g L −1 biomass and achieving up to 100% removal of total applied nitrogen and 89% COD removal. Extended nitrogen limitation during semi-continuous operation increased lipid content versus batch cultivation (56.7 vs 44.4% DW) and yielded a comparatively stable biomass composition (53.1–56.7% DW lipids; 16.3–16.5% DW protein; 27.0–30.4% DW carbohydrate) despite using feedstocks with drastically different compositions. This work provides a practical operational strategy to ensure robustness of microalgae-based BWW treatment under dynamic variability in wastewater composition. • Brewery wastewater (BWW) composition impacts Nannochloropsis growth. • Nannochloropsis efficiently treat moderate-COD BWW in batch systems. • BWW with extremely high COD inhibits Nannochloropsis growth in batch systems. • Semi-continuous cultivation overcomes COD-toxicity and stabilises biomass production. • Semi-continuous cultivation mitigates BWW variation and enhances lipid production.

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Brooke et al. (Sun,) studied this question.

synapsesocial.com/papers/69b79e7c8166e15b153abe8a https://doi.org/https://doi.org/10.1016/j.algal.2026.104648

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